title: Functional analysis of the omega-6 fatty acid desaturase (CaFAD2) gene family of the oil seed crop Crambe abyssinica.
abstract: BACKGROUND
  Crambe abyssinica produces high erucic acid (C22:1, 55-60%) in the seed oil, which can be further increased by reduction of polyunsaturated fatty acid (PUFA) levels. The omega-6 fatty acid desaturase enzyme (FAD2) is known to be involved in PUFA biosynthesis. In crambe, three CaFAD2 genes, CaFAD2-C1, CaFAD2-C2 and CaFAD2-C3 are expressed.
  
  
  RESULTS
  The individual effect of each CaFAD2 gene on oil composition was investigated through studying transgenic lines (CaFAD2-RNAi) for differential expression levels in relation to the composition of seed-oil. Six first generation transgenic plants (T1) showed C18:1 increase (by 6% to 10.5%) and PUFA reduction (by 8.6% to 10.2%). The silencing effect in these T1-plants ranged from the moderate silencing (40% to 50% reduction) of all three CaFAD2 genes to strong silencing (95% reduction) of CaFAD2-C3 alone. The progeny of two T1-plants (WG4-4 and WG19-6) was further analysed. Four or five transgene insertions are characterized in the progeny (T2) of WG19-6 in contrast to a single insertion in the T2 progeny of WG4-4. For the individual T2-plants of both families (WG19-6 and WG4-4), seed-specific silencing of CaFAD2-C1 and CaFAD2-C2 was observed in several individual T2-plants but, on average in both families, the level of silencing of these genes was not significant. A significant reduction in expression level (P < 0.01) in both families was only observed for CaFAD2-C3 together with significantly different C18:1 and PUFA levels in oil.
  
  
  CONCLUSIONS
  CaFAD2-C3 expression is highly correlated to levels of C18:1 (r = -0.78) and PUFA (r = 0.75), which suggests that CaFAD2-C3 is the most important one for changing the oil composition of crambe.
authors.affiliation: Wageningen UR Plant Breeding, P,O, Box 16, 6700, AA Wageningen, The Netherlands. robert.vanloo@wur.nl.
authors.forename: Jihua
authors.initials: J
authors.lastname: Cheng
authors.forename: Li-Hua
authors.initials: LH
authors.lastname: Zhu
authors.forename: Elma M J
authors.initials: EM
authors.lastname: Salentijn
authors.forename: Bangquan
authors.initials: B
authors.lastname: Huang
authors.forename: Jens
authors.initials: J
authors.lastname: Gruber
authors.forename: Annemarie C
authors.initials: AC
authors.lastname: Dechesne
authors.forename: Frans A
authors.initials: FA
authors.lastname: Krens
authors.forename: Weicong
authors.initials: W
authors.lastname: Qi
authors.forename: Richard G F
authors.initials: RG
authors.lastname: Visser
authors.forename: Eibertus N
authors.initials: EN
authors.lastname: van Loo
mesh_terms: D031218:Crambe Plant / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism*; D044943:Fatty Acid Desaturases / Q000235:genetics / Q000378:metabolism*; D043371:Fatty Acids, Omega-6 / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics / Q000378:metabolism
chemical_list: D043371:Fatty Acids, Omega-6; D010940:Plant Proteins; D044943:Fatty Acid Desaturases